1. Field of the Invention
The present invention relates to a method of culturing a microorganism capable of producing at least any one of a highly unsaturated fatty acid and a compound containing a highly unsaturated fatty acid as a constituent fatty acid in a medium containing at least a carbon source and a nitrogen source, using an aeration-agitation culture device capable of adjusting and controlling the agitation power and the aeration amount.
2. Description of the Related Art
In aerobic culture, a result of culture (e.g., productivity of highly unsaturated fatty acid (hereinafter referred to as “PUFA (polyunsaturated fatty acid)”), etc.) often varies depending on supply of oxygen. Therefore, in the case of scale-up, KLa (volmetric oxygen transfer coefficient) is considered to be an important index in addition to factors, such as the amount of aeration, agitation speed, and power required for aeration-agitation.
The use of KLa as an index in scaled-up culture is based on the idea that the same culture result is obtained irrespective of the type and scale of a culture vessel if the oxygen transfer rate is the same (see, for example, Non-patent Publications 1 and 2).
Various techniques for measuring KLa have been proposed, however, their operation is complicated. Cooper et al. has proposed a method of estimating KLa in a simpler manner, in which an approximate expression KLa=K(P/V)0.95(Vs)0.67 (K: proportionality constant, P: power required for agitation (W), V: liquid amount (m3), Vs: air flow rate (m/sec)) is used (see Non-patent publication 3).
(Non-patent publication 1) Satoshi Murakami et al., Kagaku Kogaku Ronbunshu (Papers of Chemical Engineering), 26(4): 557-562 (2000)
(Non-patent publication 2) A. E. Humphery, Hakko Kogaku Kaishi (Journal of Fermentation Technology), 42: 334-345 (1964)
(Non-patent publication 3) C. M. Cooper et al., Ind. Chem. Eng., 36: 504-509 (1944)